A more thorough explanation:

Instrumentum

Instrumentum is a Latin word that refers to a written document or deed that is not sealed. It can be any legal document that is used to prove something.

• A lease agreement is an example of an instrumentum because it is a written document that proves that a tenant has the right to use a property for a certain period of time.
• A promissory note is another example of an instrumentum because it is a written document that proves that someone has promised to pay back a loan.

These examples illustrate how instrumentum is used to refer to any written document that serves as proof of something. It can be used in legal proceedings to support a claim or to establish a right.